Degenerative mitral regurgitation due to leaflet prolapse is common and can be surgically repaired in the vast majority of patients, thus improving symptoms and restoring normal life expectancy. Despite the safety and efficacy of contemporary mitral valve repair, an ongoing international debate persists regarding the need for early intervention in patients without class I indications (that is, individuals with no or minimal symptoms and normal left ventricular function).

This debate is in part propagated by conflicting views of the prognostic consequences of uncorrected severe mitral regurgitation — considered as benign by those supporting medical watchful waiting (until a distinct event occurs) versus conveying excess mortality and morbidity (including heart failure and atrial fibrillation) by those advocating early surgical intervention. The controversy is further reflected in current consensus statements, which classify early mitral valve repair as a Class IIa recommendation (preponderance of evidence in favor) in North America and Class IIb (not favored) in Europe.

Watchful waiting has recently come under renewed scrutiny, however, due to emerging evidence that a growing number of centers can now achieve high (> 90 percent) mitral valve repair rates with very low operative risk (< 0.5 percent), and increasing recognition that awaiting incipient symptoms or ventricular dysfunction prior to intervention may be associated with excess long-term mortality and heart failure despite eventual rescue surgery. Although single-center data have suggested that early surgery is beneficial, the long-term consequences of currently interpreted and applied guidelines in diverse real-world tertiary care practices are unknown.

To understand the comparative effectiveness of early surgery versus initial conservative management strategies, Rakesh M. Suri, M.D., D.Phil., cardiovascular surgeon at Mayo Clinic in Rochester, Minn., Maurice Enriquez-Sarano, M.D., cardiologist at Mayo Clinic in Rochester, and co-authors from five other international centers analyzed data from the Mitral Regurgitation International Database (MIDA). This database is a multicenter, multinational registry of echocardiographically diagnosed mitral regurgitation due to flail leaflets. They tested the null hypothesis that these therapeutic approaches are associated with similar late outcomes.

"The results showed that mitral valve surgery provided significant benefits over watchful waiting once patients have severe regurgitation as documented by a reliable surrogate, the identification of a flail leaflet," says Dr. Suri, the lead author. "This is perhaps counterintuitive to patients because they often assume that they should be more severely affected before they need surgery. Actually, the opposite is true. Once a patient with severe mitral regurgitation due to flail leaflet has surgery, even without symptoms, long-term benefits are observed with only a very low upfront risk. In other words, surgery is protective in that it increases long-term survival and decreases the risk of heart failure if performed promptly following diagnosis."

In the study of 1,021 patients with severe mitral valve regurgitation without symptoms or other classical indications for surgery (heart failure or left ventricular dysfunction), 446 underwent mitral valve repair surgery within three months of diagnosis, while 575 had an initial medical monitoring while surgery remained a possible later option. Participants were followed for an average of 10 years, the longest of any previous study examining the question of when to operate.

Long-term survival rates were higher for patients who had surgery within three months of diagnosis compared with those who were medically managed for the initial three months following diagnosis (86 percent versus 69 percent at 10-year follow-up). In addition, long-term heart failure risk was lower for patients who had surgery early (7 percent versus 23 percent at 10-year follow up). There was not a difference between the two groups for late-onset atrial fibrillation, which is another concern for patients with severe mitral valve regurgitation.

"In the past, the risk of surgery and complications was greater, and watchful waiting made more sense," says Dr. Sarano. But today, referent valve centers have a greater than 95 percent success rate for mitral valve repair. In addition, the operative risk of death today is less than 0.1 percent, while it was more than 10 times higher in the 1980s. "The results were of a magnitude greater than expected and were strikingly consistent using 3 robust statistical methods," reports Dr. Suri.

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